It is known that hollow shafts, in particular those designed for rotating at high speed such as the hollow shafts of steam turbines, are subjected to careful inspection, preferably carried out by radiography or ultrasonics, in order to identify any presence in the shaft thickness of blowholes, microcracks and general defects which could give rise to dangerous fracture during service.
When said defects are found in proximity to the inner surface of the hollow shaft, it is possible to remove them by a reaming operation which locally enlarges the inner diameter of the shaft.
In this case, the reamed surface must be suitably joined into the crude inner surface of the surrounding zones in order to prevent any notching effects, which are as dangerous as the defect to be obviated.